Radio frequency (RF) filters that can be reconfigured to operate within a broad frequency range are highly desired to address the size requirements of emerging compact and multifunctional RF front-ends. The reconfigurable filter technologies that are currently being investigated mainly rely on material loadings, semiconductor varactor diodes, ferroelectric varactors, RF microelectromehanical system (MEMS) switches, and RF MEMS varactors. The performance of these filters is limited by the frequency tunability and/or power handling of their varactors. For example, the frequency tuning range of varactor diode based filters is typically below 30%. RF MEMS technology enables the fabrication of miniaturized filters, but the frequency tuning range is small unless the tuning is performed in a discrete manner. Evanescent mode cavity resonator filters controlled with MEMS-based actuators have been shown to offer a high frequency tuning range, but these filters generally exhibit large electrical sizes due to their volumetric construction.
In view of the limitations of current reconfigurable bandpass filters, it can be appreciated that it would be desirable to have alternative reconfigurable bandpass filters that do not suffer from such limitations.